Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Parathyroid hormone (PTH) alters osteoblast morphology. How these changes in cell shape modify nuclear structure and ultimately gene expression is not known. Chronic exposure to rat PTH (1-34) [10 nM] attenuated the expression of 200, 190, and 160 kD proteins in the nuclear matrix-intermediate filament subfraction of the rat osteosarcoma cells, ROS 17/2.8 [Bidwell et al. (1994b): Endocrinology 134:1738-1744]. Here, we determined that these same PTH-responsive proteins were expressed in rat metaphyseal osteoblasts. We identified the 200 kD protein as a non-muscle myosin. Although the molecular weights, subcellular distribution, and half-lives of the 190 and 160 kD proteins were similar to topoisomerase II-alpha and -beta, nuclear matrix enzymes that mediate DNA topology, the 190 and 160 kD proteins did not interact with topoisomerase antibodies. Nevertheless, the expression of topoisomerase II-alpha, and NuMA, a component of the nuclear core filaments, was also regulated by PTH in the osteosarcoma cells. The 190 kD protein was selectively expressed in bone cells as it was not observed in OK opossum kidney cells, H4 hepatoma cells, or NIH3T3 cells. PTH attenuated mRNA expression of the PTH receptor in our cell preparations. These results demonstrate that PTH selectively alters the expression of osteoblast membrane, cytoskeletal, and nucleoskeletal proteins. Topoisomerase II-alpha, NuMA, and the 190 and 160 kD proteins may direct the nuclear PTH signalling pathways to the target genes and play a structural role in osteoblast gene expression.
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PMID:Parathyroid hormone regulates the expression of rat osteoblast and osteosarcoma nuclear matrix proteins. 891 89

While astral microtubules are believed to be primarily responsible for the stimulation of cytokinesis in Echinoderm embryos, it has been suggested that a signal emanating from the chromosomal region and mediated by the interzonal microtubules stimulates cytokinesis in cultured mammalian cells. To test this hypothesis, we examined cytokinesis in normal rat kidney cells treated with an inhibitor of topoisomerase II, (+)-1,2-bis(3,5-dioxopiperaz-inyl-1-yl)propane, which prevents the separation of sister chromatids and the formation of a spindle interzone. The majority of treated cells showed various degrees of abnormality in cytokinesis. Furrows frequently deviated from the equatorial plane, twisting daughter cells into irregular shapes. Some cells developed furrows in regions outside the equator or far away from the spindle. In addition, F-actin and myosin II accumulated at the lateral ingressing margins but did not form a continuous band along the equator as in control cells. Imaging of microinjected 5- (and 6-) carboxymtetramethylrhodamine-tubulin revealed that a unique set of microtubules projected out from the chromosomal vicinity upon anaphase onset. These microtubules emanated toward the lateral cortex, where they delineated sites of microtubule bundle formation, cortical ingression, and F-actin and myosin II accumulation. As centrosome integrity and astral microtubules appeared unperturbed by (+)-1,2-bis(3, 5-dioxopiperaz-inyl-1-yl)propane treatment, the present observations cannot be easily explained by the conventional model involving astral microtubules. We suggest that in cultured epithelial cells the organization of the chromosomes dictates the organization of midzone microtubules, which in turn determines and maintains the cleavage activity.
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PMID:Inhibition of chromosomal separation provides insights into cleavage furrow stimulation in cultured epithelial cells. 969 74

The isoflavones, genistein and genistin, are cytotoxic in vitro (e.g. , inhibition of cell proliferation), due in part to inhibition of protein tyrosine kinase and DNA topoisomerase activities. Normal cell functions associated with these enzymatic activities could potentially be impaired in animals through ingestion of soybean products. In this study, cultured rat myogenic cells (L8) were used to determine whether genistein or genistin influences myoblast proliferation and fusion, and myotube protein synthesis and degradation. Genistein or genistin was dissolved in dimethylsulfoxide and included in the culture medium at 0, 1, 10 or 100 micromol/L. Myoblast proliferation was measured by methyl-3H-thymidine incorporation over 48 h. Myoblast differentiation was evaluated by the number of nuclei in multinucleated myotubes. Myotube protein synthesis was measured by 2-h 3H-amino acid incorporation into the myosin and total protein pools after acute (2 h) or chronic (24 h) exposure to similar treatments; protein degradation was measured by measuring radioactivity in protein pools following a time course of protein breakdown after myotube proteins were prelabeled with 3H-amino acids. Genistein or genistin strongly inhibited in vitro myoblast proliferation (P < 0.001) and fusion (P < 0.001) in a dose-dependent manner with effective genistein concentration as low as 1 micromol/L. Genistein or genistin inhibited protein accretion in myotubes (P < 0.001). Decreased protein accretion is largely a result of inhibition on cellular (myofibrillar) protein synthesis rate. No adverse effect on protein degradation was observed. Results suggest that if sufficient circulating concentrations are reached in tissues of animals consuming soy products, genistein/genistin can potentially affect normal muscle growth and development.
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PMID:Soybean isoflavones, genistein and genistin, inhibit rat myoblast proliferation, fusion and myotube protein synthesis. 1039 89

Molecular motors, such as kinesin, myosin, or dynein, convert chemical energy into mechanical energy by hydrolyzing ATP. The mechanical energy is used for moving in discrete steps along the cytoskeleton and carrying a molecular load. High resolution single molecule recordings of motor steps appear as a stochastic sequence of dwells, resembling a staircase. Staircase data can also be obtained from other molecular machines such as F1 -ATPase, RNA polymerase, or topoisomerase. We developed a maximum likelihood algorithm that estimates the rate constants between different conformational states of the protein, including motor steps. We model the motor with a periodic Markov model that reflects the repetitive chemistry of the motor step. We estimated the kinetics from the idealized dwell-sequence by numerical maximization of the likelihood function for discrete-time Markov models. This approach eliminates the need for missed event correction. The algorithm can fit kinetic models of arbitrary complexity, such as uniform or alternating step chemistry, reversible or irreversible kinetics, ATP concentration and mechanical force-dependent rates, etc. The method allows global fitting across stationary and nonstationary experimental conditions, and user-defined a priori constraints on rate constants. The algorithm was tested with simulated data, and implemented in the free QuB software.
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PMID:Maximum likelihood estimation of molecular motor kinetics from staircase dwell-time sequences. 1667 62

Processive molecular motors, such as kinesin, myosin, or dynein, convert chemical energy into mechanical energy by hydrolyzing ATP. The mechanical energy is used for moving in discrete steps along the cytoskeleton and carrying a molecular load. Single-molecule recordings of motor position along a substrate polymer appear as a stochastic staircase. Recordings of other single molecules, such as F1-ATPase, RNA polymerase, or topoisomerase, have the same appearance. We present a maximum likelihood algorithm that extracts the dwell time sequence from noisy data, and estimates state transition probabilities and the distribution of the motor step size. The algorithm can handle models with uniform or alternating step sizes, and reversible or irreversible kinetics. A periodic Markov model describes the repetitive chemistry of the motor, and a Kalman filter allows one to include models with variable step size and to correct for baseline drift. The data are optimized recursively and globally over single or multiple data sets, making the results objective over the full scale of the data. Local binary algorithms, such as the t-test, do not represent the behavior of the whole data set. Our method is model-based, and allows rapid testing of different models by comparing the likelihood scores. From data obtained with current technology, steps as small as 8 nm can be resolved and analyzed with our method. The kinetic consequences of the extracted dwell sequence can be further analyzed in detail. We show results from analyzing simulated and experimental kinesin and myosin motor data. The algorithm is implemented in the free QuB software.
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PMID:Extracting dwell time sequences from processive molecular motor data. 1690 7

We have presented a structural model of the chromosome based on its constituent proteins. Development of a method of mass isolation for intact human metaphase chromosomes and proteome analysis by mass spectrometry of the isolated chromosomal proteins enabled us to develop a four-layer structural model of human metaphase chromosomes. The model consists of four layers, each with different chromosomal protein sets, i.e., chromosome coating proteins (CCPs), chromosome peripheral proteins (CPPs), chromosome structural proteins (CSPs), and chromosome fibrous proteins (CFPs). More than 200 identified proteins have been classified and assigned to the four layers with each layer occupying a distinct region of the chromosome. CCPs are localized at the most outer regions of the chromosomes and they attach to the regions tentatively and occasionally. CCPs include mostly mitochondrial and cytoplasmic proteins, e.g., 70 kDa heat shock protein 9B and Hsp60. CPPs are also localized at the peripheral regions of the chromosomes, but as the essential part of the chromosomes. CPPs include nucleolin, lamin A/C, fibrillarin, etc. CSPs are the primary chromosomal structure proteins, and include topoisomerase IIalpha, condensin subunits, histones, etc. CFPs have a fibrous nature, e.g., beta-actin, vimentin, myosin II, tublin, etc. A data set of these proteins, which we developed, contains essential chromosome proteins with classified information based on this four-layer model and presents useful leads for further studies on chromosomal structure and function.
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PMID:Chromosome protein framework from proteome analysis of isolated human metaphase chromosomes. 1766 45